IgG1 plasmacytosis in interleukin 6 transgenic mice

Cytokine stimulation of prostaglandin production inhibits the proliferation of serum-stimulated mesangial cells

Mesangial cell proliferation contributes to glomerulosclerosis and is associated with the development of end-stage renal disease. We examined the effects of the cytokines interleukin 1 (IL-1 beta) and interleukin 6 (IL-6) on the mitogenesis and proliferation of rat glomerular mesangial cells. Exposure of serum-stimulated cells to IL-1 beta and IL-6 for 48 hours resulted in a dose-dependent inhibition of both mitogenesis, determined by 3H-thymidine incorporation, and proliferation, determined by absolute cell counts. Both IL-1 beta and IL-6 stimulated endogenous PGE2 production in this cell system. Cyclooxygenase inhibition by indomethacin and meclofenamate abrogated the inhibitory effects of both IL-1 beta and IL-6. Furthermore, addition of exogenous PGE2 to cytokine-stimulated cells in which cyclooxygenase activity was blocked resulted in inhibition of mitogenesis, while addition of exogenous aracidonic acid to the cytokine-stimulated cells enhanced the induced inhibition of mitogenesis. These results demonstrate that in serum-stimulated mesangial cells, both IL-1 beta and IL-6 inhibit mitogenesis and proliferation, and that these effects are mediated, in part, by stimulated endogenous prostaglandin production.

Platelet activating factor synthesis and metabolism in intestinal ischaemia-reperfusion injury

The object of this study was to characterize the synthesis and metabolism of platelet activating factor (PAF) by intestinal mucosa subjected to ischaemia–reperfusion injury. Canine intestinal mucosa produced 16:0-PAF, 18:0-PAF, and high levels of the corresponding lyso- PAF metabolites. Three h of intestinal ischaemia and ischaemia followed by 1 h of reperfusion did not affect the synthesis or metabolism of PAF by intestinal mucosa. Intestinal mucosa elaborated a factor that rapidly hydrolyzes PAF to lyso-PAF. The observed hydrolysis rate was not altered by ischaemia or ischaemia and reperfusion. In conclusion, this study suggests that intestinal mucosa produces PAF and rapidly hydrolyzes PAF. The PAF synthesis and metabolism rates of intestinal mucosa is not altered by ischaemia reperfusion in this model under the imposed conditions.

Transgenic mice in the study of cytokine function

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Glomerulosclerosis induced by in vivo transfection of transforming growth factor-beta or platelet-derived growth factor gene into the rat kidney

Glomerulosclerosis, a final common lesion of various glomerular diseases, is characterized by mesangial cell proliferation and extracellular matrix (ECM) expansion. TGF-beta and PDGF are known to play a critical role in the regulation of ECM metabolism and mesenchymal cell proliferation, respectively. However, there is little evidence to demonstrate the direct role of each of these growth factors in the pathogenesis of glomerulosclerosis. Using an in vivo transfection technique, we could realize the selective overexpression of single growth factor in the kidney. The introduction of either TGF-beta or PDGF-B gene alone into the kidney induced glomerulosclerosis, although the patterns of action of these growth factors were different; TGF-beta affected ECM accumulation rather than cell proliferation and PDGF affected the latter rather than the former.

In situ expression of cytokines in IgA nephritis

We studied mRNA and protein expression of interleukins (IL) and tumor necrosis factor (TNF) in renal tissues biopsied from 40 patients with IgA nephritis. Immunofluorescent staining with antibodies to IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF-alpha, and TNF-beta was intense in the cytoplasm of cells in glomeruli, which were dual-stained with an anti-monocyte-macrophage antibody. In addition, moderate immunofluorescence for TNF-alpha, and weak staining for IL-1 alpha and IL-6 were occasionally found in resident glomerular cells. Immunoperoxidase-in situ hybridization dual-labeling revealed that IL-1 alpha, IL-6, and TNF-alpha mRNA signals were present in intraglomerular cells reactive with anti-monocyte-macrophage antibody, which further supported the immunofluorescent findings. Cells expressing IL-1 alpha, IL-1 beta, IL-6, IL-8, TNF-alpha, and TNF-beta were also observed in the interstitium. Most of these cells were also labeled with the anti-monocyte-macrophage antibody. The number of IL-1 alpha, IL-6, and TNF-alpha-positive cells infiltrating the glomerulus significantly correlated with mesangial hypercellularity. IL-8 and TNF-alpha-positive intraglomerular cells were correlated with the magnitude of proteinuria. The population of interstitial cells positive for IL-1 alpha, IL-6, IL-8, and TNF-alpha was associated with the grade of tubulointerstitial changes and proteinuria. There was no correlation between local IL-1 alpha, IL-6, and TNF-alpha expression in glomeruli or interstitium and serum or urinary levels of the respective cytokines.(ABSTRACT TRUNCATED AT 250 WORDS)

Progenitor cell hyperplasia with rare development of myeloid leukemia in interleukin 11 bone marrow chimeras

Post 5-fluorouracil-treated murine bone marrow cells infected with a recombinant retrovirus (murine stem cell virus-interleukin 11 [MSCV-IL-11]) bearing a human IL-11 gene were transplanted into lethally irradiated syngeneic mice. Analysis of proviral integration sites in DNA prepared from hematopoietic tissues and purified cell populations of long-term reconstituted primary and secondary recipients demonstrated polyclonal engraftment by multipotential stem cells. High levels (100-1,500 U/ml) of IL-11 were detected in the plasma of the MSCV-IL-11 mice. Systemic effects of chronic IL-11 exposure included loss of body fat, thymus atrophy, some alterations in plasma protein levels, frequent inflammation of the eyelids, and often a hyperactive state. A sustained rise in peripheral platelet levels (approximately 1.5-fold) was seen throughout the observation period (4-17 wk). No changes were observed in the total number of circulating leukocytes in the majority of the transplanted animals (including 10 primary and 18 secondary recipients) despite a > 20-fold elevation in myeloid progenitor cell content in the spleen. The exceptions were members of one transplant pedigree which presented with myeloid leukemia during the secondary transplant phase. A clonal origin of the disease was determined, with significant expansion of the MSCV-IL-11-marked clone having occurred in the spleen of the primary host. Culturing of leukemic spleen cells from a quaternary recipient led to the establishment of a permanent cell line (denoted PGMD1). IL-11-producing PGMD1 myeloid leukemic cells are dependent on IL-3 for continuous growth in vitro and they differentiate into granulocytes and macrophages in response to granulocyte/macrophage colony-stimulating factor. The inability of autogenously produced IL-11 to support autonomous growth of PGMD1 cells argues against a mechanism of transformation involving a classical autocrine loop.

Up-regulation by cyclosporine (CsA) of the in vitro release of soluble CD23 (sCD23) and of the in vitro production of IL-6 and IgM

In the present study, we examined the effect of CsA on the in vitro production of Ig and on the in vitro production of molecules known to have B-cell growth and differentiation activities, such as IL-6 and sCD23. For the purpose of this study, we developed an experimental in vitro system closely resembling an in vivo model of ongoing B-cell activation. Pre-activated B cells proliferated and produced IgM optimally when they were re-cultured in the presence of IL-2/IL-6. CsA down-regulated the IL-2/IL-6-induced proliferative responses of pre-activated B cells by at least 50%, but it up-regulated IgM production in the same experiments. This up-regulating effect was not cytokine-related since it was also seen when cells were re-cultured in the absence of any cytokines. Optimal release of sCD23 was observed when SAC-pre-activated B cells were re-cultured in the presence of IL-4 or IL-4 plus IL-2 and CsA up-regulated significantly the release of this molecule in these cultures. Finally, CsA was shown to inhibit PHA-induced cell proliferation of PBMC and to up-regulate IL-6 production in the same cultures. We conclude that CsA can amplify in vitro both the production of Ig and the release of sCD23 by pre-activated B cells. This finding, in combination with the CsA-induced up-regulation of lectin-induced IL-6 production, may have clinical implications in disease states with an ongoing immune activation, where prolonged administration of CsA might be anticipated.

Expression of cytokines and growth factors in human glomerulonephritides

Numerous experimental studies point to the potential role of cytokines and growth factors in the pathogenesis of renal disease. However, from the various autocrine and paracrine mediators identified in vitro and in animal models, so far only a few have been demonstrated in selected human glomerulopathies. We examined two types of glomerulonephritis (GN): extracapillary GN with anti-neutrophil cytoplasmic autoantibodies (ANCA), an example of an acute form of GN, and mesangial IgA GN, usually a chronic form of GN, with immunocytochemistry, in situ hybridization and the polymerase chain reaction. Normal renal tissue from tumour nephrectomies served as a control. In ANCA-positive GN with active renal lesions (crescents, glomerular and vascular necrosis), infiltrating mononuclear cells in glomeruli and in the interstitium expressed interleukin (IL)-1 beta, tumour necrosis factor (TNF)-alpha, IL-2, interferon (IFN)-gamma, platelet-derived growth factor (PDGF) and transforming growth factor (TGF)-beta. Cytokine expression was also observed in activated resident cells, including endothelial cells, capsular epithelial cells, smooth muscle cells of vessel walls, fibroblasts and some tubular epithelial cells. In addition, we noted an increase in the cytokine and growth factor receptors TNF-R, IL-1R type II, IL-2R, IFN-gamma R and PDGF beta-R. In contrast, in mesangial IgA-GN, IL-1 beta, TNF-alpha, IFN-gamma and IL-2 were usually absent in glomeruli. Mesangial expansion in this disorder was accompanied by an increased expression of PDGF, PDGF beta-R, TGF-beta and IL-6 in mesangial areas. In both conditions a good correlation was observed between cytokine expression at the mRNA (in situ hybridization) and protein level (immunocytochemistry).(ABSTRACT TRUNCATED AT 250 WORDS)

TGF beta and HIV infection

TGF beta is a cytokine which is involved with the regulation of different aspects of host defense responses to injury. Overexpression of TGF beta can lead to the conversion of its protective functions to pathogenetic manifestations. TGF beta is a potent factor in promoting anabolic aspects in connective tissue metabolism, and uncontrolled production of TGF beta has been associated with the development of fibrosis. With respect to its effects on immune and inflammatory responses, TGF beta is an important endogenous immunosuppressive factor which physiologically may protect the organism from tissue damage caused by chronic activation of leukocytes. As a result of overproduction in HIV infection, this function of TGF beta can contribute to noncytopathic mechanisms of immunodeficiency. TGF beta is involved with several aspects of HIV disease and promotes virus replication and spreading through multiple distinct mechanisms. It directly stimulates virus replication in infected monocytes and peripheral blood mononuclear cells under certain in vitro conditions. It may stimulate the production of other cytokines that enhance virus replication and it may be the mediator of other HIV-stimulating agents such as cocaine. It enhances recruitment of mononuclear phagocytes as cells susceptible to virus infection. Through its profound and broad inhibitory effects on different antiviral defense mechanisms, it facilitates more rapid progression of virus infection and increases susceptibility to opportunistic infections and malignancies. Although these findings are largely based on in vitro systems, the demonstration of TGF beta overexpression in HIV-infected patients supports the notion that this cytokine is an important pathogenetic mediator in HIV infection and its associated diseases. Therapeutic strategies to interfere with these functions of TGF beta are the development of TGF beta-neutralizing antibodies and soluble TGF beta-binding proteins and receptors as well as approaches directed at reducing TGF beta gene expression.

Interleukin-6, a new target for therapy in multiple myeloma?

During the past few years much insight has been gained into the immunobiology of multiple myeloma. It has become evident that the growth of myeloma cells is regulated by cytokines, notably interleukin-6. In this paper a brief review is given of the evidence derived from in vitro as well as in vivo observations that interleukin-6 is involved in the pathogenesis of multiple myeloma, and the implications of these findings for the development of new therapeutic strategies are discussed.

Interleukin-6 cDNA transfected Lewis lung carcinoma cells show unaltered net tumour growth rate but cause weight loss and shortened survival in syngeneic mice

HuIL-6 cDNA, cloned into a neomycin resistant conferring expression vector, BMGNeo, was transfected into Lewis Lung Carcinoma (LLC) cells. LLC cells (5 x 10(6) ml-1) transfected with IL-6 cDNA (LLC-IL6) secreted IL-6 into the culture supernatant at a concentration of 9.9 ng ml-1 within 48 h. When 1,000,000 of untransfected LLC, BMGNeo vector transfected LLC (LLC-Neo) or LLC-IL6 cells were transplanted into C57BL/6 mice subcutaneously, the mean +/- s.d. of survival times of these mice were 33.3 +/- 9.7, 34.3 +/- 7.1 and 17.0 +/- 3.1 days, respectively. The survival time of LLC-IL6 cells transplanted mice was significantly shorter than that of LLC (P < 0.01) or LLC-Neo (P < 0.01) cells transplanted mice without a measurable difference of tumour size. Plasma concentration of IL-6 steadily increased in LLC-IL6 transplanted mice. Body weight and serum albumin were significantly lower in LLC-IL6 transplanted mice than in LLC transplanted mice. Mouse IL-1 alpha and mouse TNF-alpha were not detected in the plasma of LLC-IL6 transplanted mice. These data suggested that secretion of IL-6 from LLC cells was unable to alter net tumour growth rate but rather caused a state similar to cachexia without detectable increase of IL-1 alpha and TNF-alpha in the plasma. This state may be responsible for the shortened survival of LLC-IL6 tumour-bearing mice.

Soluble aggregates of IgG and immune complexes enhance IL-6 production by renal mesangial cells

Primary rat mesangial cells (MC) were cultured in RPMI-1640 containing 5% fetal calf serum (FCS). The cells produced interleukin-6 (IL-6) in vitro depending on the concentration of FCS in the medium. Binding of soluble aggregates of IgG (AIgG) to MC was visualized with AIgG coupled with aminomethyl coumarin acetic acid (AMCA). There was a dose-dependent binding of 125I-AIgG to MC at 4 degrees C. Scatchard analysis revealed binding of AIgG containing 20 to 24 molecules per aggregate, with an affinity of 2.2 x 10(8) M-1 and a total average number of 2.7 x 10(5) sites per cell. The binding of AIgG or immune complexes to MC resulted in enhanced production of IL-6 by MC in culture. This enhanced production of IL-6 was dependent on the concentration of AIgG. To our surprise, preparations of monomeric IgG (mIgG) also enhanced the production of IL-6 by MC, but to a lower extent when compared to levels induced by AIgG. Very little amounts of aggregated F(ab')2 fragments [AF(ab')2] bound to MC and consequently no significant enhancement of IL-6 release by AF(ab')2 was seen, suggesting that IL-6 production is an Fc receptor-mediated phenomenon. The production of IL-6 by MC is inhibitable by cycloheximide, thus indicating de novo synthesis. Northern blot analysis revealed a threefold increase in mRNA for IL-6 by AIgG in vitro. The increase in mRNA expression was directly related to the quantity of IL-6 released in the supernatant by MC. These results suggest that binding of AIgG or immune complexes to MC in vivo may induce IL-6 production by MC, thus leading to proliferation of MC.

Cytokine-induced changes in the leukon

Cytokines are regulatory peptides, produced by virtually every nucleated cell type in the body, that have pleiotropic effects on hematopoietic, lymphoid, and other cell types. Cytokines usually act locally as autocrine or paracrine cellular signals intended to maintain local homeostasis but in disease states can spill over into the circulation to initiate systemic reactions. The systemic administration of high doses of recombinant cytokines is associated with a multitude of pharmacologic and toxicologic effects, frequently involving the hemolymphopoietic system. These effects may represent direct or indirect pharmacologic or hyperpharmacologic activity or may represent toxicity. The objective of this review is to present the general types of hemolymphopoietic changes associated with cytokine administration to animals and to provide examples of cytokine-induced effects on the hemolymphopoietic system.

Low molecular weight thymic factor inhibits histamine release from basophils

Low molecular weight thymic factor stimulates the suppressor function of T-lymphocytes, increases cAMP content (but not cGMP) in lymphocytes and inhibits histamine release from sensitized basophils. The mechanisms of LTF action are discussed.

B-cell activation following murine cytomegalovirus infection: implications for autoimmunity

Infection of susceptible mice with murine cytomegalovirus (MCMV) induces persistent inflammation, and the production of autoantibodies reactive with large numbers of proteins from all major organs. However the roles of polyclonal B-cell activation, autoreactive T-helper cells and host-virus cross-reactions in these phenomena have not been evaluated. The present study reveals six- to 20-fold increases in serum immunoglobulin levels in MCMV-infected BALB/c and CBA mice, with IgG3 and IgG2b most affected. Titres of antibodies reactive with autologous tissues and ovalbumin (OVA) also increased following MCMV infection, whilst responses to a synthetic antigen [polyvinyl pyrrolidone (PVP)] were unaffected or depressed. IgG2a was the isotype most affected in responses to OVA, MCMV antigens and autologous tissues, suggesting interferon-gamma (IFN-gamma) may contribute to responses induced in the presence of the relevant antigen. Increases in total and antigen-specific immunoglobulin levels were CD4 dependent, as they were reduced in infected mice depleted of these cells with anti-CD4 antibodies. Serological changes were preceded by B-cell expansion and activation evident from increased cell yields, frequencies of cells releasing immunoglobulin and proliferation of T-depleted spleen and lymph node preparations. Numbers of mature B cells and macrophages increased in the lymph nodes, but B-1a (CD5+ Ig+) cell counts remained low. Alterations in the B-cell phenotypic profiles were more complex in the spleen, but correction for increased cell yields revealed increases in some subpopulations.

Interleukin-6 and its receptor: a paradigm for cytokines

Many cytokines and cytokine receptors involved in the regulation of hematopoiesis, immune responses, and inflammation have been identified and characterized at the molecular level. Several characteristic features of cytokines, such as pleiotropy and redundancy, are now more clearly understood on the basis of their molecular structures. Accumulating evidence has demonstrated an intimate link between cytokines and various diseases such as allergy, autoimmune diseases, and cancer. The pathogenesis of these diseases and therapies to treat them will be discussed based on insights derived from cytokine research.

Transplantable myeloproliferative disease induced in mice by an interleukin 6 retrovirus

Lethally irradiated mice transplanted with bone marrow cells infected with a novel recombinant retrovirus (murine stem cell virus-interleukin 6 [MSCV-IL-6]) bearing a mouse IL-6 gene developed a fatal myeloproliferative disease within 4 wk of engraftment. The hematologic manifestations of the syndrome included elevated peripheral leukocyte counts (up to 430 x 10(3) cells/mm3) with a predominance of neutrophilic granulocytes, microcytic anemia, and thrombocytosis or thrombocytopenia. The mice showed extensive neutrophil infiltration of the lungs, liver, and occasionally lymph nodes, plus splenomegaly resulting from enhanced splenic myelopoiesis (30-60-fold increase in progenitor numbers). Despite the chronic stimulation of neutrophil excess by IL-6, bone marrow from affected mice was capable of repopulating the hematopoietic tissues (bone marrow and spleen) of lethally irradiated hosts during repeated serial transplantation. In the longest documented case, the progeny of a single MSCV-IL-6-marked cell transferred the myeloproliferative disease to two secondary, four tertiary, and two quaternary recipients (the clone endured for a total of 72 wk). These results, demonstrating considerable proliferative longevity of the IL-6-producing cells, support an in vivo role of IL-6 in the maintenance of hematopoietic precursors. Dysregulated IL-6 production also had significant systemic effects. The mice displayed increased mesangial cell proliferation in the kidney, frequent liver abnormalities, and marked alterations in plasma protein levels. Unlike previous studies where constitutive expression of exogenous IL-6 genes resulted in lymphoproliferative disorders characterized by massive plasmacytosis, minimal plasma cell expansion occurred in the MSCV-IL-6 mice during the observation period. Potential explanations for the differences in disease phenotypes observed in the present and previous studies are different cell types expressing the exogenous IL-6 genes, higher sustained circulating levels of IL-6 achieved using the MSCV-IL-6 retroviral delivery system, and/or the premature death (3-15 wk after transplantation) of the MSCV-IL-6 mice before the onset of plasmacytosis. This animal model should prove useful for further investigation of the function of IL-6 in normal and abnormal hematopoiesis and in inflammatory responses.

Long-term consequences of interleukin-6 overexpression in transgenic mice

With the aim of using interleukin-6 (IL-6)-inducible promoters to express transgenes, we investigated the long-term consequences of high levels of IL-6 in mice. As a first step, we generated transgenic mice constitutively expressing the murine IL-6 at a level sufficient to induce IL-6-responsive genes. These mice were analyzed with respect to the indirect and direct consequences of elevated IL-6 expression over a time period of about 2 years. Although biologically active IL-6 was expressed from the transgene and different alterations could be documented (less immature B cells in bone marrow, expression of IL-6-inducible liver genes), the mice appeared healthy and could easily be used for breeding. Only in mice older than 18 months did we find a high incidence of lymphomas associated with different tissues. These results indicate that the side effects of long-term treatment with IL-6 are relatively moderate, and that IL-6 might be used to mediate the expression of heterologous genes in the context of functional studies.

Pathology of the human mesangium in situ

Mesangial cells play an important role in the development and progression of human glomerular disease. This article summarizes some important aspects of mesangial properties and behaviour in situ. Intrinsic mesangial cells express alpha-smooth muscle actin and are best characterized as myofibroblasts or glomerular pericytes. The main integrin receptor in the mesangium is the alpha 1 beta 1 integrin. The beta 2 and beta 3 integrins have not been detected. Mesangial cells in situ fail to react with many monoclonal antibodies which stain human mesangial cells in culture, including leukocyte activation antigens. Prominent reactions in glomerular disease are mesangial expansion and progressive glomerular sclerosis, which are preceded by or associated with mesangial cell hypertrophy and/or proliferation. Mesangial enlargement is accompanied by an altered integrin expression and an abnormal composition of extracellular mesangial matrix. From the numerous autocrine and paracrine mediators identified in vitro which stimulate or inhibit mesangial cell growth and extracellular matrix synthesis, up to now only a few factors have been shown to be present in selected human glomerulopathies. These include platelet derived growth factors and platelet derived growth factor receptor beta, transforming growth factors beta, interleukin 1 beta, tumor necrosis factor alpha, and interleukin 6. Further identification of such mediators in situ will improve our understanding of pathological glomerular processes, particularly with respect to the multifunctional properties of the mesangial cell.

Extramedullary plasmacytoma of the thyroid, associated with follicular colonization and stromal deposition of polytypic immunoglobulins and major histocompatibility antigens. Possible categorization in MALT lymphoma

A 78-year-old woman complaining of a neck mass underwent right hemithyroidectomy. The 7 x 6 cm thyroid tumor consisted predominantly of mildly atypical, epithelial membrane antigen-positive plasma cells and scattered lymphoid follicles. Features of follicular colonization (plasma cell infiltration into germinal centers) were noted. Numerous CD45RO-positive reactive T cells and a smaller number of CD20-positive blast-like B cells were also distributed among the plasma cell infiltrate. IgG, kappa-type monoclonality with J-chain reactivity was identified in the plasma cells, including those in the lymphoid follicles. The association of pre-existing lymphocytic thyroiditis was confirmed histologically in the non-tumorous thyroid tissue. The tumor exhibited deposition of reticulin fiber-rich, amorphous eosinophilic substances, provoking pronounced foreign body reactions. The deposit, polytypically immunoreactive for immunoglobulin gamma-, mu-, kappa- and lambda-chains, beta 2-microglobulin and HLA-DR, was scarcely reactive upon amyloid staining, and consisted ultrastructurally of electron-dense, non-fibrillar material and entrapped collagen fibers. Multiple myeloma was ruled out by laboratory, histologic and clinical examinations. The possible categorization of this extramedullary plasmacytoma of the thyroid within low-grade B cell lymphoma of the mucosa-associated lymphoid tissue (MALT) is discussed.

Mesangial cell-matrix interactions. Effects on mesangial cell growth and cytokine secretion

Glomerulonephritis (GN) results in proliferation of mesangial cells (MC), infiltration of inflammatory cells, and accumulation of extracellular matrix (ECM) proteins in the mesangium. Locally secreted cytokines may stimulate MC growth or the secretion of inflammatory mediators by MC. Interleukin-6 (IL-6) may be an autocrine cofactor in the pathogenesis of mesangioproliferative GN. We studied the regulation of IL-6 secretion by MC in response to MC-derived cytokines and ECM proteins. IL-6 secretion is stimulated in a dose-dependent manner by IL-1 alpha, TNF-alpha, and PDGF. Constitutive and LPS-induced release of IL-6 by MCs is reduced on collagen type I (coll I) compared-with uncoated surfaces. IL-6 release on collagen type IV (coll IV), however, is enhanced. In addition, MC on coll I exhibit a sixfold higher growth rate than cells on uncoated surfaces. The reduction of cytokine secretion in parallel with the stimulation of MC growth by coll I suggests that exposure to coll I may result in a change from secretory to proliferative phenotype in vitro.

Hyperimmunoglobulinemia in HIV-1 infected individuals does not clearly correlate with plasma levels of IL-6

In this study we evaluated interleukin-6 (IL-6) plasma levels in 80 human immunodeficiency virus type 1 (HIV-1) seropositive (+) individuals and 51 HIV-1 seronegative (-) blood donors. Plasma IL-6, detectable only in a subset of HIV-1(+) individuals (45 of 80) and normal blood donors (28 of 51), was significantly (p less than 0.01) increased in HIV-1(+) subjects 187 +/- 20.5 vs. 86.3 +/- 14 pg/ml). Among HIV-1-infected individuals, ARC/AIDS patients showed the highest IL-6 values (243.3 +/- 43.3 pg/ml). HIV-1(+) subjects showed, at all the different stages of the disease, a significant increase in total gammaglobulins, particularly IgG (2071 +/- 101 vs 1265 +/- 34 of HIV-1 seronegative controls). Although among HIV-1-infected individuals, the group with detectable plasma levels of IL-6 shows the highest levels of IgG (2243 +/- 146 vs. 1790 +/- 105, p less than 0.05), no positive correlations were observed between plasma levels of IL-6 and total gamma globulins (r = 0.2) or IgG (0.17). IL-6 production was also examined in the endotoxin-free supernatants of peripheral blood cultured monocytes and CD4+ T lymphocytes, in the presence or absence of specific stimuli. The amount of IL-6 released in monocyte and CD4+ T-lymphocyte culture supernatants was similar in 40 HIV-1(+) individuals and 35 HIV-1(-) controls. Our data show that plasma levels of IL-6 are significantly increased in HIV-1-infected individuals, in particular in ARC/AIDS patients. However, such an increase does not strictly correlate with the degree of hypergammaglobulinemia in the same HIV-1-infected individuals.

Interleukin 6: insights to its function in skin by overexpression in transgenic mice

Interleukin 6 (IL-6) is a cytokine that mediates a wide range of inflammatory and immune responses. Its expression is elevated in inflammatory or immunodeficient diseases, including psoriasis, rheumatoid arthritis, and AIDS. To explore the role of IL-6 in skin, we utilized a human keratin 14 (K14) promoter to express IL-6 in the basal cells of stratified squamous epithelia of transgenic mice. Mice expressing the K14-IL-6 transgene were smaller than normal and exhibited retarded hair growth. Surprisingly, IL-6 expression did not lead to enhanced epidermal proliferation, but it did result in a thicker stratum corneum, with an otherwise seemingly normal program of differentiation. IL-6 expression did not lead to leukocytic infiltration, making it unlikely that it has direct proinflammatory activity in skin. Based on this study, one role of IL-6 relevant to host defense may be to enhance the stratum corneum, thereby providing increased protection from injurious stimuli or infection. If IL-6 plays additional roles in the skin, it is likely to act synergistically with factors that IL-6 alone cannot induce.

IL-6 and NF-IL6 in acute-phase response and viral infection

NF-IL6 was originally identified as a DNA-binding protein responsible for IL-1-stimulated IL-6 induction. Direct cloning of NF-IL6 revealed its homology with C/EBP. C/EBP is expressed in liver and adipose tissues and is supposed to regulate several hepatocyte- and adipocyte-specific genes. In contrast, NF-IL6 is suppressed in normal tissues, but is rapidly and drastically induced by LPS or inflammatory cytokines such as IL-1, TNF, and IL-6. NF-IL6 can also bind to the regulatory region of various genes including IL-8, G-CSF, IL-1 and immunoglobulin genes. Furthermore, NF-IL6 is shown to be identical to IL-6DBP, a DNA-binding protein responsible for IL-6-mediated induction in acute-phase proteins, demonstrating that NF-IL6 is responsible for the genes regulated by IL-6. These results indicate that NF-IL6 may be a pleiotropic mediator of many inducible genes involved in acute, immune, and inflammatory responses, like NFkB. In this regard, it is noteworthy that both an NF-IL6 binding site and an NFkB binding site are present in the inducible genes such as IL-6, IL-8, and several acute-phase genes. On the other hand, accumulating evidence has revealed that overproduction of IL-6 may be responsible for the pathogenesis and/or several symptoms of a variety of diseases, including autoimmune diseases, malignancies, and viral diseases. At present, the molecular mechanisms of abnormal expression of the IL-6 gene are not known. Recently it has become evident that interplays between viral proteins and cellular proteins play an important role in viral oncogenesis and infection. The fact that NF-IL6 binds to the enhancer core sequences of various viruses strongly suggests a possible relationship of virus infection and IL-6 expression. In fact some evidence (Mahe et al. 1991, Spergel et al. 1992) indicates that NF-IL6 may interact with viral gene enhancers or viral products, although there are no definite data about the involvement of NF-IL6 in viral pathogenesis. Future studies will be required to clarify whether or not the interplay between NF-IL6 and viral infection is responsible for deregulation of the IL-6 gene.

Continuous anti-interleukin 10 antibody administration depletes mice of Ly-1 B cells but not conventional B cells

Ly-1 B cells have the distinctive property of continuous self-replenishment and, as we have shown previously, can be further distinguished from conventional B cells on the basis of greatly elevated constitutive and inducible production of the recently described cytokine interleukin 10 (IL-10). To test the possibility that IL-10 acts as either an autocrine or paracrine growth factor for Ly-1 B cells, we treated mice continuously from birth to 8 wk of age with a monoclonal rat IgM antibody that specifically neutralizes mouse IL-10. Mice treated in this way lacked peritoneal-resident Ly-1 B cells, contained greatly reduced serum immunoglobulin M levels, and were unable to generate significant in vivo antibody responses to intraperitoneal injections of alpha 1,3-dextran or phosphorylcholine, antigens for which specific B cells reside in the Ly-1 B cell subset. In contrast, conventional splenic B cells of anti-IL-10-treated mice were normal with respect to total numbers, phenotype, and in vitro responsiveness to B cell mitogens and the thymus-dependent antigen trinitrophenyl-keyhole limpet hemocyanin (TNP-KLH). The mechanism of Ly-1 B cell depletion appeared to be related to elevation of endogenous interferon gamma (IFN-gamma) levels in anti-IL-10-treated mice, since coadministration of neutralizing anti-IFN-gamma antibodies substantially restored the number of peritoneal-resident Ly-1 B cells in these mice. These results implicate IL-10 as a regulator of Ly-1 B cell development, and identify a procedure to specifically deplete Ly-1 B cells, thereby allowing further evaluation of the role of these cells in the immune system.

Ectopic lymphokine gene expression in human peripheral blood lymphocytes in vivo

An animal model to study the effects of ectopic expression of cytokines involved in cell growth and differentiation has been established. Retrovirus vectors containing the human interleukin 6 cDNA were used to produce high titer virus-producing lines. Human peripheral blood lymphocytes (hPBLs) were successfully infected with the retrovirus and engrafted into severe combined immunodeficient mice. The majority of the animals were engrafted with hPBLs, as determined by the presence of human glucose phosphate isomerase. Furthermore, six of seven mice engrafted with hPBLs infected with high titer virus and detectable hPBLs present in the spleen expressed the retroviral human interleukin 6 gene. Importantly, human interleukin 6 protein was expressed at physiologically significant levels in these mice. These results demonstrate that models for human disease and immunotherapy involving retrovirus-mediated gene transfer into human cells can be developed in mice.

Nodular sclerosing Hodgkin's disease showing positive reaction for anti-IL 6/BSF2 antibody

A 53-year-old man presented with bilateral cervical lymph node swelling and low fever. Swollen lymph node was biopsied, and diagnosed as nodular sclerosing Hodgkin's disease (HD). By combined radio- and chemotherapy, he went into complete remission. After 3 years, fever of 38-39.2 degrees C and lymph node swelling appeared in the para-aortic region and later became systemic. A biopsy was diagnosed as syncytial variant of HD with aid of immunohistochemistry on frozen sections. Large atypical mono- or binucleated cells reacted with anti-interleukin 6 (IL-6) antibody. The patient's disease progressed with fever, and he died 66 months after the onset of disease. A previous biochemical study showed that IL-6 displayed a real relation to the generation of fever. Therefore it is suggested that fever in this patient is related to IL-6.

Glycosylation of interleukin-6 purified from normal human blood mononuclear cells

Interleukin 6 (IL-6) is a glycosylated cytokine which is important in exerting cell-specific growth-inducing, growth-inhibiting and differentiation-inducing effects. IL-6 produced in mammalian cell lines is heterogeneous, reflecting specific cell-type-dependent post-translational modifications. Native IL-6 was purified from human blood mononuclear cells and the oligosaccharides released, radiolabelled and sequenced by a combination of sequential exoglycosidase digestion using Bio-Gel P-4 high-resolution gel chromatography and acetolysis. N- and O-linked glycans were found. The N-linked glycans were sialylated di- and tri-antennary complex-type and oligomannose-type structures. However, the most predominant N-linked oligosaccharide was a small tetrasaccharide with the sequence Man alpha 6Man beta 4GlcNAc beta 4GlcNAc. This is the first report of this structure on a circulating glycoprotein. This structure has only previously been reported to be present on the syncytiotrophoblast of human placenta. The presence of the oligomannose structures and the mannose-terminating tetrasaccharide on IL-6 may be important in maintaining a high local concentration of the cytokine while limiting its systemic serum level via interaction with soluble mannose-binding serum lectins.

Enhancement of in vitro and in vivo antigen-specific antibody responses by interleukin 11

The availability of large quantities of highly purified recombinant interleukin 11 (rhuIL-11) has allowed us to investigate the effects of rhuIL-11 on sheep red blood cell (SRBC)-specific antibody responses in the murine system. The results showed that rhuIL-11 was effective in enhancing the generation of mouse spleen SRBC-specific plaque-forming cells (PFC) in the in vitro cell culture system in a dose-dependent manner. These effects of rhuIL-11 were abrogated completely by the addition of anti-rhuIL-11 antibody, but not by the addition of preimmunized rabbit serum. Cell-depletion studies revealed that L3T4 (CD4)+ T cells, but not Lyt-2 (CD8)+ T cells, are required in the rhuIL-11-stimulated augmentation of SRBC-specific antibody responses. The effects of rhuIL-11 on the SRBC-specific antibody responses in vivo were also examined. RhuIL-11 administration to normal C3H/HeJ mice resulted in a dose-dependent increase in the number of spleen SRBC-specific PFC as well as serum SRBC-specific antibody titer in both the primary and secondary immune responses. In mice immunosuppressed by cyclophosphamide treatment, rhuIL-11 administration significantly augmented the number of spleen SRBC-specific PFC as well as serum SRBC-specific antibody titer when compared with the cyclophosphamide-treated mice without IL-11 treatment. These results demonstrated that IL-11 is a novel cytokine involved in modulating antigen-specific antibody responses in vitro as well as in vivo.

Generation of plasmacytomas with the chromosomal translocation t(12;15) in interleukin 6 transgenic mice

The mechanisms through which pristane or mineral oil can induce plasmacytomas in BALB/c or NZB mice are not fully understood, but involvement of interleukin 6 (IL-6), a growth factor for plasmacytomas and myelomas, has been strongly suggested. To clarify the role of IL-6 in plasmacytomagenesis, a human IL-6 cDNA was introduced into mouse germ lines under the transcriptional control of the murine major histocompatibility complex class I (H-2Ld) promoter. IL-6 transgenic mice of C57BL/6 origin developed a massive plasmacytosis but not plasmacytomas. However, introduction of BALB/c genetic background into IL-6 transgenic mice could generate monoclonal transplantable plasmacytomas with the chromosomal translocation t(12;15). These results provide firm evidence of the critical role of IL-6 in the plasmacytoma development.

Cytokines and autoimmune disease

A wide array of cytokines are locally present in autoimmune lesions where they are produced by inflammatory cells or by the target cell of the autoimmune attack. The presence of cytokines at the site of autoaggression reflects ongoing inflammatory and activation processes. These mediators exert proinflammatory effects, contribute to the activation and stimulation of the effector function of T or B lymphocytes, directly participate in target cell destruction, and mediate accompanying local reactions, including fibrotic processes. The release of cytokines into the circulation may explain certain systemic reactions, including fever or changes in the profile of plasma proteins. Many, especially systemic, autoimmune diseases are accompanied by a dysregulation of lymphokine secretion at the level of circulating leukocytes or cells situated outside of the local inflammatory event, thus reflecting regulatory disorders that may either have a genetic or an acquired basis. Decreased production of lymphokines in vitro in response to nonspecific stimuli may be accompanied by an elevated spontaneous release in vivo resulting in an increase of circulating cytokine levels (interleukin 2, tumor necrosis factor-alpha). Secretion of interleukin 1, interleukin 2, and tumor necrosis factors-alpha or -beta, in part, is determined by genetic factors and it is possible that a particular secretor phenotype may predispose to the development of autoimmune lesions. Probably due to their pleiotropic nature, systemic administration of cytokines such as interleukin 1, interleukin 2, tumor necrosis factor, and interferon-gamma may exert either accelerating or suppressive effects on autoimmune diseases. Conversely, agents that block the function of the lymphokine interleukin 2 exert an unequivocal autoimmune disease-inhibiting effect.

Mitogenic effect of platelet-derived growth factor in human glomerular mesangial cells: modulation and/or suppression by inflammatory cytokines

Glomerular mesangial cell proliferation constitutes a frequent pathological alteration in glomerulonephritis. In addition to platelet-derived growth factor (PDGF) inflammatory cytokines such as IL-1, IL-6 or tumour necrosis factor-alpha (TNF-alpha) have been proposed to have mitogenic activity for mesangial cells. A model was therefore established in which human mesangial cells (HMC) could be reversibly growth-arrested for prolonged times in serum-free medium without suffering irreversible functional or morphological changes. In this model 24 h stimulation with rhPDGF-BB induced an increase of the 3H-thymidine incorporation of 1190 +/- 280 (50 ng/ml) % +/- s.e.m. of medium control. Less growth induction was noted after stimulation with 50 ng/ml rhPDGF-AB (925 +/- 126%) or rhPDGF-AA (575 +/- 24%). Northern analysis confirmed the presence of both alpha- and beta-PDGF receptor subunit mRNA in growth-arrested HMCs. rhIL-1 alpha, rhIL-1 beta, rhTNF-alpha or rhIL-6 at various doses and times, despite increasing cellular PGE2-release, did not induce significant proliferation in HMCs. Inhibition of PGE2-release did not change the lack of mitogenicity of IL-1, TNF-alpha or IL-6. IL-6 did not alter the mitogenic response of the cells towards PDGF. In contrast, both IL-1 alpha and IL-1 beta (5 ng/ml) induced a delay but not augmentation of the PDGF growth response. This delay could be reversed by the concomitant addition of recombinant IL-6 or of anti-IL-1 antibody but not by inhibition of prostaglandin synthesis. High doses of TNF-alpha suppressed PDGF-induced proliferation. These data suggest that in growth-arrested HMCs inflammatory cytokines have a growth-modulating or -suppressive rather than (co-)mitogenic effect while PDGF-BB and -AB and to a lesser degree PDGF-AA are potent mitogens. The findings support the notion that the control of HMC proliferation in pathological situations depends on a complex network of interacting stimuli.

Urinary IL-6: a marker for mesangial proliferative glomerulonephritis?

A prospective study of plasma and urinary interleukin-6 (IL-6) levels was performed in 54 patients undergoing renal biopsy to determine whether detectable urinary IL-6 was a reliable marker for mesangial proliferation. Interleukin-6 was found in both the urine and plasma of seven patients, the urine alone of 15 patients, and the plasma alone of two patients. Interleukin-6 was not detected in the urine or the plasma of the remaining 30 patients, the urine of 10 healthy controls or the urine of 10 patients with rheumatoid arthritis with raised plasma IL-6. Interleukin-6 was found in the urine of only one out of an additional seven patients with lupus nephritis. Urinary IL-6 was associated with a variety of renal abnormalities and was not restricted to those with mesangial hypercellularity. Furthermore, many patients with mesangial hypercellularity did not have detectable urinary IL-6. There was no correlation between urinary IL-6 and plasma IL-6, urinary albumin excretion or urinary creatinine. These results suggest that IL-6 detected in the urine is a marker of renal IL-6 production, but not specifically of mesangial hypercellularity. The patients with IL-6 in the urine had a mean serum creatinine significantly higher than those without IL-6. It is not possible to distinguish at present whether IL-6 contributes to renal dysfunction or whether it reflects renal damage.

Analysis of the immune system with transgenic mice: B cell development and lymphokines

Over the last decade transgenic mice expressing genes relevant for the immune system have been generated. Transgenic expression of immunoglobulin heavy and/or light chain genes of different isotypes and different specificities have helped to better understand phenomena relevant to B cell development such as allelic exclusion of immunoglobulins and B cell tolerance. Transgenic mice expressing interleukin genes have also been used to study the ways of action of these important growth and differentiation factors in the context of the mouse immune system.

Interleukin-6 antisense oligonucleotides inhibit the growth of human myeloma cell lines

IL-6 has been shown to be a plasmacytoma growth factor in mice and is believed to play a key role in the development of human multiple myeloma. We investigated the IL-6 requirements for the growth of two human myeloma cell lines, U 266 and RPMI 8226. These cell lines secreted minute amounts of IL-6 (20 U/ml) and featured IL-6 mRNA. IL-6 receptors were detectable at the surface of malignant cells by immunofluorescence. Antibodies to IL-6 did not alter the proliferation of these myeloma cells. There was a dose-dependent decrease, however, in [3H]-thymidine uptake in the presence of IL-6 antisense (and not sense) oligodeoxynucleotides; in the presence of 20 microM IL-6 antisense, an 80 and 95% inhibition of the proliferation of U 266 and RPMI 8226 cells was observed, respectively. These results provide strong evidence for an IL-6 autocrine proliferation of myeloma cells which may occur via internal interaction between IL-6 and the IL-6 receptor.